Chronic treatment of guinea pigs with kanamycin 100 mg/kg/day for 14 days revealed no morphological changes in the inner ear. This same treatment with kanamycin plus, on the last day, one dose of Ethacrynic acid 10 mg/kg/day and Sodium salicylate 100 mg/kg/day also did not result in any morphological changes. Therefore, chronic treatment of healthy guinea pigs with the above-mentioned drugs in low doses reveals no permanent loss of hair cells. This finding is contrary to the electrophysiologic results (published earlier) showing significant decline in cochlear potentials after treatment with Kanamycin and Ethacrynic acid given in the dosage used for the above histological studies. Combination of nontoxic doses of Kanamycin and Ethacrynic acid produced only acute changes which were most probably temporary, as 3 weeks after treatment no morphological changes were seen in the Corti organ.